1. Field of the Invention
The present invention relates to an operation control apparatus, and method of a linear compressor, and more particularly, to an operation control apparatus and method of a linear compressor that are capable of controlling a motor by turning on/off power of a controller of a linear compressor through a main controller of a refrigerator, capable of restraining an abnormal operation and improving a performance of a motor by compensating an error of a stroke voltage, and capable of removing a noise signal generated at an instantaneous power failure of a switching control signal generated from a microcomputer controlling the linear compressor.
2. Description of the Background Art
In general, a linear compressor generates a rotational torque by ON/OFF controlling power supplied to a coil wound on a multi-phase stator by using a switching device. Accordingly, by sequentially varying an excitation state between a rotor and the stator of a motor, a forward rotational torque  be generated according to a magnetic suction force.
If a specific excitation state of the motor is not varied, the rotor may be stopped at a certain position, and various driving control can be possibly made to generate a reverse rotatory force by controlling a phase of an input pulse signal applied to the switching device by taking a maximum inductance as an origin. As such, the motor is adopted for use in electronic products which need a direction control. Especially, a linear compressor used for a refrigerator or an air-conditioner, a compression ratio can be varied by a voltage applied to the motor, and thus, its cooling force can be variably controlled according to an intention of a user.
The operation control apparatus of a linear compressor in accordance with a conventional art will now be described.
FIG. 1 is a circuit diagram showing the construction of an operation control apparatus of a linear compressor in accordance with a conventional art.
As shown, the conventional operation control apparatus of a linear compressor includes: a linear compressing unit (L.COMP) for controlling a cooling force by vertically moving a piston and varying a stroke by an AC power voltage applied to an internal motor (M); a current detecting unit 20 for detecting a current applied to the linear compressing unit (L.COMP) as the stroke increases by the applied voltage; a voltage detecting unit 30 for detecting a voltage generated at the linear compressor (L.COMP) as the stroke increases by the applied voltage; a microcomputer 40 for calculating a stroke of a certain time point with the current and the voltage respectively detected by the current detecting unit 20 and the voltage detecting unit 30, comparing the stroke at the certain time point and a reference stroke command value, and outputting a switching control signal according to the comparison value; and an electric circuit unit 10 for applying a voltage to the linear compressing unit (L.COMP) by ON/OFF controlling an input AC power voltage through a triac (Tr1) according to the switching control signal of the microcomputer 40.
The operation of the conventional operation control apparatus of a linear compressor constructed as described will now be explained.
To begin with, in the linear compressor (L.COMP), the piston is vertically moved by the applied voltage according to a stroke command value set by a user, according to which the stroke is varied to control a cooling force.
In the electric circuit unit 10, as the turn-on period of the triac (Tr1) is lengthened by the switching control signal of the microcomputer, a stroke increase, and at this time, the current and the voltage applied to the motor (M) of the linear compressing unit (L.COMP) are respectively detected by the current detecting unit 20 and the voltage detecting unit 30 and inputted to the microcomputer 40.
The microcomputer 40 calculates a stroke at a certain time point by using the applied current and the applied voltage detected by the current detecting unit 20 and the voltage detecting unit 30, compares the stroke with a reference stroke command value, and outputs a switching control signal according to the comparison value. If the stroke at the certain time point is smaller than the reference stroke command value, the microcomputer 40 outputs a switching control signal for lengthening the ON period of the triac (Tr1) to increase the voltage applied to the linear compressing unit (L.COMP).
If, however, the stroke at the certain time point is greater than the reference stroke command value, the microcomputer 50 outputs a switching control signal for shortening the ON period of the triac (Tr1) to reduce the voltage applied to the linear compressing unit (L.COMP), thereby driving the motor (M) of the linear compressing unit (L.COMP).
FIG. 2 is a waveform of the current applied to the linear compressing unit of FIG. 1.
As the triac (Tr1) of the electric circuit unit 10 is turned on by the microcomputer 40, the current applied to the linear compressing unit (L.COMP) has a certain waveform. The motor (M) of the linear compressing unit (L.COMP) performs a compressing stroke at the positive (+) current and an expanding stroke at the negative stroke.
In case that a refrigerator operates, when portion of moisture contained in a food item is circulated along with a cooking air inside the refrigerator, it is frozen at an evaporator, forming frost. The frost is sensed by a defrosting sensor (not shown) mounted at the evaporator and removed as a defrosting heater is heated according to a defrosting operation. At this time, the defrosting operation is performed with a stroke distance reduced.
FIG. 3 is an exemplary view showing a compressing unit of a general linear compressor.
As shown, the compressing unit of the conventional linear compressor includes: a cylinder 10 hollowed with a certain inner diameter; a piston 20 inserted into the cylinder and reciprocally and linearly moved upon receiving a driving force of the motor; a discharge cover 30 coupled at one side of the cylinder 10 to cover the section of the piston 20 inserted in the cylinder 10 and a compression space (P) formed in the cylinder 10; a discharge valve 40 inserted in the discharge cover 30 and opening and closing the compression space (P) of the cylinder 10; and a valve spring 50 for elastically supporting the interior of the discharge cover 30 and the discharge valve 40.
However, during the defrosting operation of the refrigerator, the refrigerator is overloaded therein, and according to a temperature change inside the refrigerator, the piston 20 is escaped from the cylinder 10 after passing an upper dead center and gets into the discharge cover 30, to collide with and damage the discharge valve 40.
In addition, an error occurs inevitably during a calculation of the stroke voltage with the output voltage and the output current applied to the microcomputer 40. Therefore, it is not possible to precisely control the motor (MO of the linear compressing unit (L.COMP), and the motor is abnormally operated and its performance is degraded.
Moreover, when the compressor is instantly turned on/off (power failure), a gate signal is generated to turn on the triac (Tr1) regardless of a triac (Tr1) operation signal in the microcomputer 40, resulting in a malfunction of the linear compressor.